On Mon, Sep 04, 2017 at 08:49:44AM -0700, Darrick J. Wong wrote:
> If we have speculative cow preallocations hanging around in the cow
> fork, don't let a truncate operation clear the reflink flag because if
> we do then there's a chance we'll forget to free those extents when we
> destroy the incore inode.
>
> Reported-by: Amir Goldstein <amir73il@xxxxxxxxx>
> Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> ---
> fs/xfs/xfs_inode.c | 8 +++++---
> 1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
> index 5599dda..4ec5b7f 100644
> --- a/fs/xfs/xfs_inode.c
> +++ b/fs/xfs/xfs_inode.c
> @@ -1624,10 +1624,12 @@ xfs_itruncate_extents(
> goto out;
>
> /*
> - * Clear the reflink flag if we truncated everything.
> + * Clear the reflink flag if there are no data fork blocks and
> + * there are no extents staged in the cow fork.
> */
> - if (ip->i_d.di_nblocks == 0 && xfs_is_reflink_inode(ip)) {
> - ip->i_d.di_flags2 &= ~XFS_DIFLAG2_REFLINK;
> + if (xfs_is_reflink_inode(ip) && ip->i_cnextents == 0) {
> + if (ip->i_d.di_nblocks == 0)
> + ip->i_d.di_flags2 &= ~XFS_DIFLAG2_REFLINK;
> xfs_inode_clear_cowblocks_tag(ip);
This part looks ok:
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
But while looking at that I decided I'd want to take a look at
other places where we potentially clear XFS_DIFLAG2_REFLINK.
In xfs_ioctl_setattr_xflags it seems like it's not currently safe
for setting the RT flag vs having COW extents? I also think we'd
need the iolock for every change to the rt flag, so this probably
needs a bigger rework..
swapext also doesn't seem to flush out existing cow extents.
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